1. Field of the Invention
This invention relates to the cross-breeding of a novel variety of barley which has been found to have the unexpected property that the starch granules recovered therefrom are self-liquefying without the addition of any further quantities of enzymes.
2. Description of the Prior Art
Starch is usually obtained in the form of granules by separation from starch-containing plants or plant parts. In most manufacturing processes which utilize starch, such as in the brewing of beer, the preparation of confectionary, paper manufacture or the like, the starch is first pasted and then liquefied by cleavage of the starch molecule to reduce the viscosity of the paste. The granules are initially insoluble in water, but when heated in water, they begin to swell, imbibing water rapidly until they are many times their original size. Upon continued heating, the granules begin to disintegrate and the viscosity of the water-starch mixture beings to rapidly increase until it reaches a maximum, thereby forming a paste. If the starch is a waxy starch, as is the starch of the present invention, further heating after the maximum viscosity is reached results in an initial drop in viscosity. However, cooling of the partially solubilized paste causes the hydrated molecules and segments of granules to insolubilize, forming a paste probably through H-bonding of starch chains. In the case of normal starch, this paste, on cooling, will form a stiff gel. Waxy starches will remain somewhat fluid. This initial cooking phase usually requires heating to temperatures in the range of 85.degree.-105.degree. C., depending upon the particular variety of starch being treated. In this critical cooking phase, viscosities as low as 300-400 Brabender viscosity units (B.U.) are attainable. However, under microscopic examination, the granules will show a substantial increase in size.
The pasted starch can then be treated in many ways, such as by acid treatment to effect a conversion of the starch directly to sugars or dextrins or by molecular cleavage by acid or enzymes. It also can be oxidized or cross-linked to prepare special starch derivatives.
In enzyme conversion, the enzymes rupture bonds in the starch, resulting in a reduction in molecular weight. Liquefication is said to occur when a starch paste containing 8% starch dry basis shows a Brabender viscosity in the range of 0-20 units. However, the exact extent of liquefication will be determined by the particular application for the starch.
One of the largest uses of starch is for coating paper where it increases the strength, causes the fiber to lay down, makes the surface better able to take ink for printing and increases resistance to wetting. For this purpose, starch is added to water, heated to boiling or run through a pressure cooker, cooled to conversion temperature, commercial enzyme added and the starch held until the viscosity reaches the desired point, which is determined by time of flow through a special pipette. At this point the mixture is rapidly heated to boiling to denature the enzyme.
It would be desirable, however, to provide a starch which has a much lower pasting temperature than known starches, so that the period for heating to effect pasting can be reduced. Likewise, if a starch could be developed which is self liquefying, the preliminary cooking step now being used, could be eliminated.
In the past, where it has been desired to liquefy the paste, such as in brewing, enzyme conversion to liquefy the paste was accomplished by addition of an enzyme into the paste followed by mild heating. For instance, to make a liquefied product suitable for beer brewing, a malt infusion was first prepared which contained a high percentage of .alpha.-amylase, which the infusion was added to the starch paste.
In normal brewing operations, part of the barley malt is added to the adjunct (corn starch, rice, or corn grits) and the mixture heated to boiling. During the heating process, the starch is gelatinized and partially converted; however, the enzyme is destroyed before the process is completed. The cooked adjunct is then added to the main malt mash which is heated to 65.degree. C., held for a half hour and then gradually heated to 75.degree. C. where it is maintained for 3-4 hours in order to convert and extract as much material as possible.
It is known that although natural cereal grains do not contain substantial amounts of .alpha.-amylase, the quantity (activity) of the enzyme in the starch upon germination (malting) increases by factors of from 2000 to 10,000. That is, the units of activity of the enzyme of barley goes from 0.045 before malting to 90.0 after malting. Unfortunately, this high enzyme content is ordinarily lost during extraction and in the initial cooking phase of most starches.
It was long recognized that if the enzyme could be protected during these initial processing stages, then a self-liquefying starch could be obtained which would not require the addition of further enzymes to the starch paste. However, heretofore no satisfactory technique for protecting the enzyme has been developed. For instance, consideration was given to bind the enzyme by lime water treatment so that it is not steeped from the grains too quickly, or by formaldehyde treatment or the like. None of these techniques, however, has proven to be commercially acceptable or to protect a large enough percentage of the enzymes.
If a starch granule could be developed which would be self-liquefying without the addition of further enzymes, or, even more desirably, without cooking, the industrial demand for such a starch source would be quite significant. The starch source could be useable as a replacement for corn syrup in the brewing industry and, if the source were prepared from barley grain, it would have a substantially lower cost and, hence, would be quite competitive with corn syrup. Since it would enable the elimination of at least one and possibly two processing steps normally required for the utilization of starch, it would be highly advantageous in a wide variety of applications.